Among multilayer ceramic capacitors (MLCCs), ferroelectric ceramic capacitors utilize a ferroelectric ceramic material (barium titanate) that causes the ceramic capacitor to expand and contract when a voltage is applied due to the piezoelectric effect (electrostrictive effect).
The expansion and contraction (vibration) of the ceramic capacitor is conveyed to the circuit board, causing it to vibrate. This can produce an audible sound when the vibration frequency is within the range of human hearing (20 Hz to 20 kHz). This phenomenon is referred to as the emission of “acoustic noise” by the ceramic capacitor.
The “acoustic noise” phenomenon in ceramic capacitors involves vibration with an amplitude of only 1 pm to 1 nm, and it is not thought to pose any reliability problems for the ceramic capacitors themselves or for adjacent components.
The following Murata products incorporate measures to reduce acoustic noise:
For general consumer applications, the ZRA and ZRB series, and the KRM and KR3 with metal terminals are available.
For automotive applications, the KCM and KC3 series are available. Please visit pages linked to below for details.